The present invention relates to an actuating mechanism for a pivoting door thrust reverser for a turbojet engine.
Turbofan-type turbojet engines are well known in the art and typically comprise a fan at the front of the turbojet engine which directs a flow of bypass air through a duct bounded by the engine cowling on the inside and a fan cowling on the outside. The generally annular duct bounded by the engine cowling and the fan cowling may channel both the bypass flow and the primary exhaust gas flow at a downstream portion or may channel only the bypass flow.
In aircraft on which the turbojet engine is mounted outside of the airframe structure, the fan cowling and the engine cowling are configured to form boundaries of the bypass flow duct and to provide aerodynamic outer surfaces to reduce drag.
FIG. 1 illustrates a known pivoting door-type thrust reverser associated with the cowling of a turbojet engine. As illustrated, the forward portion of the fan cowling 1 defines the outer limits of the bypass flow duct and is generally concentrically arranged about the turbojet engine (not shown). The cowling 1 comprises an external cowling panel and an internal cowling panel interconnected by a front frame 6. The outer surface of the external cowling panel has an aerodynamic surface over which the air external to the engine passes during aircraft flight. The inner surface of the inner cowling panel defines the outer boundary of a gas flow duct.
The cowling also comprises a thrust reverser comprising a door 7 pivotally attached to the cowling such that it is movable between a closed, forward thrust position, illustrated in FIG. 1, and an open, reverse thrust position in which the upstream end (towards the left as viewed in FIG. 1) of the thrust reverser door 7 is moved outwardly from the cowling, while a downstream portion is moved inwardly into the gas flow duct airstream so as to redirect at least a portion of the gas flow through an opening in the cowling in a direction that has a reverse thrust component.
An actuator 4 for moving the door 7 between its forward and reverse thrust positions may comprise an actuating cylinder mounted to the front frame 6, and have an extendable and retractable piston rod connected to the thrust reverser door 7.
The upstream end 11 of the door 7 may have a deflector 13 to maximize the efficiency of the thrust reverser when the door 7 is in the reverse thrust position. When the door is in the forward thrust position, as illustrated in FIG. 1, an outer surface panel is substantially flush with the external surfaces of the cowling. Door 7 may have a cavity or recess 12 to accommodate the actuator 4 when the door is in the forward thrust position.
A plurality of thrust reverser doors 7 may be incorporated into the cowling, such doors being circumferentially spaced around the periphery of the cowling. A portion of the cowling axially extends between forward and rear portions of the cowling between circumferentially adjacent thrust reverser doors 7 to provide structural rigidity to the fan cowling and to provide pivot mounting points for attaching the doors 7 to the fan cowling. French Patents 1,482,538 and 2,030,034 illustrate typical, known thrust reversers.
U.S. Pat. No. 3,605,411 discloses a pivoting door-type thrust reverser in which the deflector mounted on the upstream or forward end of the thrust reverser door is movable to an extended position when the door is in the reverse thrust position.
French Patent 2,618,853 discloses a thrust reverser in which the deflector is retracted when the door is in its forward thrust position to optimize engine performance.
In some applications, as illustrated in FIG. 1, the deflector 13 projects from the inner surface of the thrust reverser door 7 even when the door is in its forward thrust position without extending into the gas flow duct. This forms a cavity facing inwardly into the gas flow duct which will slightly degrade engine performance.
French Patent 2,680,547 discloses a thrust reverser having a combination of spoilers and deflectors to attempt to optimize the direction of exhaust flow.
French Patent 1,482,538 also illustrates that it is known to drive the thrust reverser door between its forward thrust position and reverse thrust position using a linear actuator in which each door is associated with one linear actuator affixed by its forward portion to the stationary portion of the cowling.
For engineering simplicity, the linear actuator may incorporate a locking function acting on the movable rod of the linear actuator to lock the thrust reverser door in the forward thrust position. Because of the travel of the rod, the location of the locking system may be either on the forward portion, or the rear portion of the actuator.
The length of the linear actuator is determined by the kinematics of the thrust reverser door, the loads imposed upon the door and the positioning of the locking system, the length generally being very large compared to the surrounding structural environment which requires the mounting of the linear actuator through the front frame of the stationary structure of the thrust reverser. Because of this location of the linear actuator, several structural problems arise. As illustrated in FIG. 1, in order not to interrupt the interfacing shroud between the thrust reverser and the engine, the linear actuator is placed in a radially intermediate zone of the front frame structure 6. The resulting force F1 of the linear actuator 4 on the thrust reverser door 7 and the distance L1 between the force and the engagement interface of the mounting flange 3 on the interface bracket 5 produces a large twisting torque MI on the front frame structure. A second problem is that the swivel mount allowing the linear actuator to swivel relative to the front frame 6 is located around the linear actuator body and mounted on the front frame 6, thereby necessitating a large aperture to be formed in the front frame 6. These two problems are significant and require reinforcing of the front frame 6. Such reinforcement increases the weight of the overall system and does not fully eliminate the twisting torque problem.
The positioning of the linear actuator also causes a third problem. The location of the actuating fluid supply and return lines, which may be flexible, are located forwardly of the front frame 6, close by the combustion chamber and high temperature areas of the jet engine, thereby raising the possibility of fire should any leaks occur.